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Wishbone seat stay suspension

2417 Views 10 Replies 6 Participants Last post by  seat_boy
I'm thinking of building a frame with wishbone seat stays. I'm inclined to install a coil shock between the wishbone and the seat tube. The leverage ratio on this suspension would be linear, but this is more about comfort than performance. Think nature trails; not jumps and drops. The single pivot would be just above the BB and another pivot point where each seat stay connects to the corresponding chain stay. The chain stays act as the swing arm, and the seat stays change length thanks to the coil spring above the wishbone. Has anyone seen or tried this kind of approach?
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How much travel? Moots, has been doing short travel pivotless wishbone suspension since 1991 on their titanium YBB frames, and before that on steel. I can remember some KHS softail frames and Litespeed Unicoi frames that also had either a spring or a shock at the wishbone. I don't know what their pivot setup looked like, if there were pivots. The GT LTS was a longer travel and more complicated version of this.
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The Moots and KHS were pivotless designs.

If all you are after is some comfort on bike paths, a suspension seatpost would probably be a much better way to spend your money. I did a 3-day tour on washboard dirt roads on a loaner bike with a Cane Creek Thudbuster. It was glorious.
Very interesting designs! I was unaware of those previously, so thank you for shedding some light. It looks like the pivotless design suits short, undampened travel.

The GT LTS is a thing of beauty. If you took out the rocker linkage and made it linear, that's closer to what I was imagining.

It's really about where to mount the shock on/in the frame. I hate when the shocks take up space in the front triangle. Plus, mounting it at the wishbone connection might let me get even weirder. It would be cool to have a modular system where I could remove the shock altogether and have a spacer that allows me to ride hardtail. Or better yet, an adjustable spacer to accommodate different tire sizes, BB heights, etc. Different shocks could be swapped in or out depending on mood (and budget).
Yes, the soft tails are short travel and pivotless. However some were available with a damped shock.

For another linkage rear end similar to the LTS, search for the Specialized M2 Stumpjumper.

For more of a linear design inspiration with pivots, look at the Proflex bikes from the early 90's. Their lower end bikes (300-400 series) used regular chainstays and a traditional looking diamond frame shape with an inline urethane spring while their higher end bikes used elevated chainstays. Originally all of the models came with urethane bumpers but later there were some damped shocks used.

One thing that you have to deal with in having a linear design is a very small amount of space in which to have your shock fit between the seat tube and the rear wheel, especially if you go 29er. The builder of my small frame soft tail 29er had to use a taller than necessary seat tube in order to fit the suspension slider between the wheel and seat tube and then renforce the seat tube to the top tube on the front.

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Proflex! That's exactly what I'm looking for in the rear triangle in terms of the design. Thank you!

I'm still unsure if a concentric BB pivot would be better, or an elevated chainstay pivot just above the BB would be better. I also wonder about some of these older suspension designs. The shock tech and material science has progressed so much in the last few decades. An older/simpler suspension design might be more performant with new shocks because it can rely on the shock itself to do the heavy lifting (pun intended).
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The Specialized Ground Control was probably the closest design to what you'd like to do.
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The Specialized Ground Control was probably the closest design to what you'd like to do.
That is the one I was trying to think of.
Thanks @dr.welby! Hope all is well with you!
The Moots and KHS were pivotless designs.

If all you are after is some comfort on bike paths, a suspension seatpost would probably be a much better way to spend your money. I did a 3-day tour on washboard dirt

roads on a loaner bike with a Cane Creek Thudbuster. It was glorious.






You can get a good bike loan at directloantransfer
newbie question incoming

NY the"loaner bike" you mean that you get the bike on a loan, so basically rented it?
newbie question incoming

NY the"loaner bike" you mean that you get the bike on a loan, so basically rented it?
It was loaned to me as part of a media junket.
The Salsa Dos Niner was another type of pivotless rear travel with a tiny rear shock behind the seat tube. A frame well known for breaking.
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